XML 57 R45.htm IDEA: XBRL DOCUMENT v3.7.0.1
Intangible Assets - Carrying Amount of Goodwill Allocated by Domestic and Foreign Operations (Detail) - USD ($)
$ in Millions
Jun. 30, 2017
Dec. 31, 2016
Goodwill [Line Items]    
Total goodwill - net $ 3,989.0 $ 3,767.8
Unites States [Member]    
Goodwill [Line Items]    
Total goodwill - net 2,274.2 2,138.5
United Kingdom [Member]    
Goodwill [Line Items]    
Total goodwill - net 699.2 666.5
Canada [Member]    
Goodwill [Line Items]    
Total goodwill - net 295.8 292.2
Australia [Member]    
Goodwill [Line Items]    
Total goodwill - net 405.8 382.7
New Zealand [Member]    
Goodwill [Line Items]    
Total goodwill - net 224.7 205.3
Other Foreign [Member]    
Goodwill [Line Items]    
Total goodwill - net 89.3 82.6
Brokerage [Member]    
Goodwill [Line Items]    
Total goodwill - net 3,946.0 3,736.9
Brokerage [Member] | Unites States [Member]    
Goodwill [Line Items]    
Total goodwill - net 2,250.7 2,115.0
Brokerage [Member] | United Kingdom [Member]    
Goodwill [Line Items]    
Total goodwill - net 692.4 662.2
Brokerage [Member] | Canada [Member]    
Goodwill [Line Items]    
Total goodwill - net 295.8 292.2
Brokerage [Member] | Australia [Member]    
Goodwill [Line Items]    
Total goodwill - net 405.8 382.7
Brokerage [Member] | New Zealand [Member]    
Goodwill [Line Items]    
Total goodwill - net 214.9 205.0
Brokerage [Member] | Other Foreign [Member]    
Goodwill [Line Items]    
Total goodwill - net 86.4 79.8
Risk Management [Member]    
Goodwill [Line Items]    
Total goodwill - net 40.1 28.1
Risk Management [Member] | Unites States [Member]    
Goodwill [Line Items]    
Total goodwill - net 23.5 23.5
Risk Management [Member] | United Kingdom [Member]    
Goodwill [Line Items]    
Total goodwill - net 6.8 4.3
Risk Management [Member] | New Zealand [Member]    
Goodwill [Line Items]    
Total goodwill - net 9.8 0.3
Corporate [Member]    
Goodwill [Line Items]    
Total goodwill - net 2.9 2.8
Corporate [Member] | Other Foreign [Member]    
Goodwill [Line Items]    
Total goodwill - net $ 2.9 $ 2.8